"Dancing with the Stars" Signs Rob Kardashian

Multiple sources confirm ... Rob Kardashian is officially on board -- despite concerns about the "Dancing" schedule conflicting with Kim's super MEGA wedding in August. We're told the two sides addressed the issue and hammered out a plan -- and Rob signed on the dotted line.

Rob will be the 2nd Kardashian to compete on the show -- his sister Kim hit the ballroom in 2008 ... but she was eliminated just 3 weeks in to the competition.